1. Filed of the Invention
The present invention relates to an antenna switch module, an all-in-one communication module, a communication apparatus and a method for manufacturing the antenna switch module. For instance, it relates to antenna switch modules for high-frequency and high-power signals.
2. Related Art of the Invention
In recent years, there has been a demand for a portable telephone supporting a multi band capable of using a plurality of methods. The reason for this is an expanding user base of mobile communication such as portable telephones and globalization. For instance, there is a demand for a triple-band portable telephone using three communication methods of different frequency bands of ESGM (Enhanced-Global System for Mobile Communication) method mainly used in Europe, a DCS (Digital Cellular System) method increasingly used in conjunction with the expanding user base of portable telephones and a PCS (Personal Communication Services) method mainly used in the U.S.A. Furthermore, there is a demand for a quad-band portable telephone adding UMTS (Universal Mobile Telecommunication System) which implements next-generation high-speed communication.
For that reason, development is underway antenna switches using FET switches comprised of GaAs-field-effect transistors (hereafter, FETs) capable of easily supporting the trend toward multi band.
As shown in FIG. 19, an antenna switch 40 in the prior art has a semiconductor chip 46 mounted on a surface of a dielectric layered body 45, and the semiconductor chip 46 is mounted on a land electrode pattern for dies bond formed on the dielectric layered body 45 (refer to Japanese Patent Laid-Open No. 2001-285112, pp. 3 to 4, FIGS. 1 and 4, for instance). The disclosure of the above document is incorporated herein by reference in its entirety. The portion indicated by a dashed line in the upper portion of the dielectric layered body 45 in FIG. 19 is the portion to be resin-sealed, and FIG. 19 is a diagram seeing through this resin 44 portion. In addition, the semiconductor chip 46 is comprised of one semiconductor chip. However, it may be comprised of two or more separate semiconductor chips for a switch portion and a logic portion.
FIG. 7 is an equivalent circuit diagram of FET switch operating as SPST (Single-Pole Single-Throw) which is a very basic antenna switch circuit. In an FET switch 10 indicated by a range enclosed by an alternate long and short dash line in FIG. 7, an FET 16 providing a shunt circuit is connected to ground via a capacitor 17. The FET switch 10 in the prior art used as the capacitor 17 an MIM (Metal-Insulator-Metal) capacitor formed in the semiconductor chip.
The capacitor 17 is formed in the semiconductor chip by using the MIM capacitor for the following reason. To be more specific, if an impedance between the FET of the shunt circuit and the ground in the antenna switch circuit becomes high, a ground potential of the FET of the shunt circuit becomes high on operation and a high-frequency characteristic deteriorates. Thus, as shown in FIG. 7, wiring Ls1 between the FET 16 and the capacitor 17 is rendered as small as possible in order to reduce a parasitic inductance contributing to the impedance due to a wiring Ls between the FET and the ground for the sake of preventing the impedance from becoming higher. In the case of mounting the capacitor 17 on the top surface of the dielectric layered body 45, the wiring routed on the dielectric layered body 45 becomes so long that a distance L1 cannot be short. For that reason, the capacitor 17 is formed in the semiconductor chip in which the FET is formed so as to render the wiring Ls1 shortest, and thus a wiring L shortest.
The above-mentioned antenna switch in the prior art uses an MIM capacitor formed in the semiconductor chip as a capacitor for connecting an FET of a shunt circuit to a ground. The MIM capacitor is generally a parallel plate type capacitor sandwiching an insulator such as SiO2 or SiN of 0.2 to 0.3 μm thickness with a conductive material such as Au. Therefore, there is a problem that, if an electrostatic surge of 300V or so gets in from the outside, the capacitor connected to the FET of the shunt circuit is destroyed so that it no longer functions as the switch.
The present invention resolves the problem in the prior art, and an object thereof is to provide an antenna switch module, an all-in-one communication module, a communication apparatus and a method for manufacturing the antenna switch module, wherein the capacitor is not destroyed and a high-frequency characteristic does not deteriorate even in the case where a high-voltage signal such as the electrostatic surge flows in.